Answer:
The nictitating membrane, also known as the third eyelid, is a transparent membrane that helps to protect the eyes of frogs. It is located on the inner corner of the eye and can be drawn across the eye to protect it from dust, mud, and water. The nictitating membrane also helps to keep the eyes moist.
The nictitating membrane is not unique to frogs; it is also found in other amphibians, reptiles, birds, and some mammals. In humans, the nictitating membrane is a vestigial organ, meaning that it no longer serves a functional purpose.
Step-by-step explanation:
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining vision.
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining vision. The term comes from the Latin word nictare, meaning "to blink". It is often called a third eyelid or haw, and may be referred to in scientific terminology as the plica semilunaris, membrana nictitans, or palpebra tertia. Unlike the upper and lower eyelids, the nictitating membrane moves horizontally across the eyeball.
In frogs, the nictitating membrane serves several important functions:
- It protects the eye from dust, mud, and water.
- It helps to keep the eye moist.
- It helps to spread tears evenly across the eye.
- It helps to remove irritants from the eye.
- It helps to protect the eye from the sun's ultraviolet rays.
The nictitating membrane is also found in other amphibians, reptiles, birds, and some mammals. In humans, the nictitating membrane is a vestigial organ, meaning that it no longer serves a functional purpose.